Method for Executing Migration Between Virtual Servers and Server System Used for the Same

1. A method for executing migration in an information processing system including: at least one server system that accesses a storage apparatus in response to a request transmitted from a client device; and a plurality of virtual servers which are implemented in the server system, the method allowing execution of migration between the plurality of virtual servers, the method allowing the server system to execute the steps of: storing an amount of resources of the server system that are usable for executing migration, storing a plurality of policies each defining how to execute a corresponding one of a plurality of migrations, and including information for specifying a resource use amount of the server system to be used to execute the migration, for each of the policies, obtaining the resource use amount needed to execute the migration according to the policy, allocating an amount of usable resources to each of the policies in accordance with the resource use amount obtained for the policy, in the migration according to each of the policies, allocating a certain amount of resources usable for executing the migration, to the virtual server which serves as either of a migration destination and a migration source, the certain amount of resources being determined within the amount of resources allocated to the policy, and executing the migration according to each of the policies in accordance with the resource use amount allocated to the policy, wherein the information for specifying a resource use amount of the server system to be used to execute the migration includes any one of the number of data to be moved in the migration and a data size of the data to be moved.

2. The method for executing migration according to claim 1 , wherein the server system includes a CPU, a memory, a first communication adapter for communicating with another server system, and a second communication adapter for communicating with the storage apparatus, if the virtual server serving as a data migration source and the virtual server serving as a data migration destination in the execution of the migration exist in the same server system, the resources allocated between the virtual servers include the CPU, the memory, and the second communication adapter, if the virtual server serving as a data migration source and the virtual server serving as a data migration destination in the execution of the migration exist in the different server systems, respectively, the resources allocated between the virtual servers include the CPU, the first communication adapter, and the second communication adapter, for each of the policies, the server system pre-stores the resource use amount according to data size of data to be moved in the migration from the virtual server serving as a data migration source to the virtual server serving as a data migration destination, for each of the policies, the server system obtains the resource use amount needed to execute the migration according to the policy, based on the pre-stored resource use amount according to data size, the server system obtains the resource use amount according to data size needed to execute the migration from the virtual server serving as a data migration source to the virtual server serving as a data migration destination, by actually migrating test data there between according to the policy, the information for specifying a resource use amount of the server system to be used to execute the migration includes any one of the number of data to be moved in the migration and a data size of the data to be moved, when the amount of resources of the server system usable for executing migration changes during the migration, the server system changes the amount of resources allocated between the virtual servers within the amount of resources of the server system after the change, by re-executing the step of allocating an amount of usable resources to each of the policies in accordance with the resource use amount obtained for the policy, and the step of, in the migration according to each of the policies, allocating a certain amount of resources usable for executing the migration, to the virtual server which serves as either of a migration destination and a migration source, the certain amount of resources being determined within the amount of resources allocated to the policy, each of the virtual servers has a file system, the storage apparatus has a function of backing up data using a block transfer scheme on a logical volume basis, in the migration, the virtual server serving as a migration source in the migration deletes, from the storage apparatus, a file entity managed in the storage apparatus by the virtual server serving as a data migration source itself, and stores, in that storage apparatus, a stub including information specifying a migration destination of the file, the virtual server stores the stub in a specific logical volume in the storage apparatus, the server system provides a virtual volume created using thin provisioning, for management of data in the storage apparatus, in the migration, the virtual server serving as a migration source in the migration deletes, from the storage apparatus, a file entity managed in the storage apparatus by the virtual server serving as a data migration source itself, and stores, in that storage apparatus, a stub including information specifying a migration destination of the file, and in the deletion of the file entity, the virtual server issues a command to release a storage area of the logical volume previously used to store the file entity thus deleted.

3. The method for executing migration according to claim 1 , wherein the server system includes a CPU, a memory, a first communication adapter for communicating with another server system, and a second communication adapter for communicating with the storage apparatus, if the virtual server serving as a data migration source and the virtual server serving as a data migration destination in the execution of the migration exist in the same server system, the resources allocated between the virtual servers include the CPU, the memory, and the second communication adapter, and if the virtual server serving as a data migration source and the virtual server serving as a data migration destination in the execution of the migration exist in the different server systems, respectively, the resources allocated between the virtual servers include the CPU, the first communication adapter, and the second communication adapter.

4. The method for executing migration according to claim 1 , wherein for each of the policies, the server system pre-stores the resource use amount according to data size of data to be moved in the migration from the virtual server serving as a data migration source to the virtual server serving as a data migration destination, and for each of the policies, the server system obtains the resource use amount needed to execute the migration according to the policy, based on the pre-stored resource use amount according to data size.

5. The method for executing migration according to claim 4 , wherein the server system obtains the resource use amount according to data size needed to execute the migration from the virtual server serving as a data migration source to the virtual server serving as a data migration destination, by actually migrating test data there between according to the policy.

6. The method for executing migration according to claim 1 , wherein when the amount of resources of the server system usable for executing migration changes during the migration, the server system changes the amount of resources allocated between the virtual servers within the amount of resources of the server system after the change, by re-executing the step of allocating an amount of usable resources to each of the policies in accordance with the resource use amount obtained for the policy, and the step of, in the migration according to each of the policies, allocating a certain amount of resources usable for executing the migration, to the virtual server which serves as either of a migration destination and a migration source, the certain amount of resources being determined within the amount of resources allocated to the policy.

7. The method for executing migration according to claim 1 , wherein each of the virtual servers has a file system, the storage apparatus has a function of backing up data using a block transfer scheme on a logical volume basis, in the migration, the virtual server serving as a migration source in the migration deletes, from the storage apparatus, a file entity managed in the storage apparatus by the virtual server serving as a data migration source itself, and stores, in that storage apparatus, a stub including information specifying a migration destination of the file, and the virtual server stores the stub in a specific logical volume in the storage apparatus.

8. The method for executing migration according to claim 1 , wherein each of the virtual servers has a file system, the server system provides a virtual volume created using thin provisioning, for management of data in the storage apparatus, in the migration, the virtual server serving as a migration source in the migration deletes, from the storage apparatus, a file entity managed in the storage apparatus by the virtual server serving as a data migration source itself, and stores, in that storage apparatus, a stub including information specifying a migration destination of the file, and in the deletion of the file entity, the virtual server issues a command to release a storage area of the logical volume previously used to store the file entity thus deleted.

9. A server system in an information processing system including: at least one server system that accesses a storage apparatus in response to a request transmitted from a client device; and a plurality of virtual servers implemented in the server system, wherein the server system: stores an amount of resources of the server system that are usable for executing migration, stores a plurality of policies each defining how to execute a corresponding one of a plurality of migrations, and including information for specifying a resource use amount of the server system to be used to execute the migration, for each of the policies, obtains the resource use amount needed to execute the migration according to the policy, and allocates an amount of usable resources to each of the policies in accordance with the resource use amount obtained for the policy, in the migration according to each of the policies, allocates a certain amount of resources usable for executing the migration, to the virtual server which serves as either of a migration destination and a migration source, the certain amount of resources being determined within the amount of resources allocated to the policy, and executes the migration according to each of the policies in accordance with the resource use amount allocated to the policy, wherein the information for specifying a resource use amount of the server system to be used to execute the migration includes any one of the number of data to be moved in the migration and a data size of the data to be moved.

10. The server system according to claim 9 , comprising a CPU, a memory, a first communication adapter for communicating with another server system, and a second communication adapter for communicating with the storage apparatus, wherein if the virtual server serving as a data migration source and the virtual server serving as a data migration destination in the execution of the migration exist in the same server system, the resources allocated between the virtual servers include the CPU, the memory, and the second communication adapter, and if the virtual server serving as a data migration source and the virtual server serving as a data migration destination in the execution of the migration exist in the different server systems, respectively, the resources allocated between the virtual servers include the CPU, the first communication adapter, and the second communication adapter.

11. The server system according to claim 9 , wherein for each of the policies, the resource use amount according to data size of data is pre-stored, the data size of data being to be moved in the migration from the virtual server serving as a data migration source to the virtual server serving as a data migration destination, for each of the policies, the resource use amount needed to execute the migration according to the policy is obtained based on the pre-stored resource use amount according to data size, and the resource use amount according to data size needed to execute the migration from the virtual server serving as a data migration source to the virtual server serving as a data migration destination is obtained by actually migrating test data there between according to the policy.

12. The server system according to claim 9 , wherein when the amount of resources of the server system usable for executing migration changes during the migration, the amount of resources allocated between the virtual servers is changed within the amount of resources of the server system after the change, by re-executing the allocation, to each of the policies, of an amount of usable resources in accordance with the resource use amount obtained for the policy, and the allocation, in the migration according to each of the policies, of a certain amount of resources usable for executing the migration, to the virtual server which serves as either of a migration destination and a migration source, the certain amount of resources being determined within the amount of resources allocated to the policy.

13. The server system according to claim 9 , wherein each of the virtual servers has a file system, the storage apparatus has a function of backing up data using a block transfer scheme on a logical volume basis, in the migration, the virtual server serving as a migration source in the migration deletes, from the storage apparatus, a file entity managed in the storage apparatus by the virtual server serving as a data migration source itself, and stores, in that storage apparatus, a stub including information specifying a migration destination of the file, and the virtual server stores the stub in a specific logical volume in the storage apparatus.

14. The server system according to claim 9 , wherein each of the virtual servers has a file system, the server system provides a virtual volume created using thin provisioning, for management of data in the storage apparatus, in the migration, the virtual server serving as a migration source in the migration deletes, from the storage apparatus, a file entity managed in the storage apparatus by the virtual server serving as a data migration source itself, and stores, in that storage apparatus, a stub including information specifying a migration destination of the file, and in the deletion of the file entity, the virtual server issues a command to release a storage area of the logical volume previously used to store the file entity thus deleted.